As a trained health geographer with expertise in the areas of social-ecological models, neighborhood effects, and Geographic Information System, I am further interested in expanding my research foci in the interface of substance abuse and HIV/AIDS, both from methodological and intervention perspectives. To that end, in the upcoming five years of training, I will devote my time to focused research on multidimensional correlates to adherence, retention, and HIV treatment outcomes among infected drug users using system science techniques. The ultimate goal is to design interventions to improve HIV treatment outcomes among this vulnerable population. To achieve this goal, I will work with an internationally recognized group of mentors to obtain training in the epidemiology of substance use disorders, HIV transmission and treatment, social network analysis, and design of interventions. My specific objectives to achieve this career goal are: 1. Enhance my background and understanding of existing literature on behavioral and clinical interventions to seek, test, treat, and retain in care among drug users with HIV infection. 2. A. Advance expertise in theory, visualization, and application of social network analysis, including egocentric network, whole network, and longitudinal networks. Incorporate spatial dependency to innovatively advance social network metrics to spatial-social network metrics. B. Develop expertise in research methods necessary to design, perform, and evaluate randomized controlled trials. 3. Gain experience in intervention development, testing, implementation, and dissemination that will address multidimensional barriers to adherence and retention in care among HIV positive drug users. 4. Development of an independent career path in behavioral intervention-oriented research focused on the intersection between substance abuse and HIV by successfully writing and receipt of a R01 grant. Given the vital importance of mentoring in the process of training and career development, I have assembled a strong interdisciplinary panel of mentors and consultants who will provide guidance throughout my five years of advanced training. Dr. Frederick Altice will serve as my primary mentor (substance abuse, HIV, intervention), with Drs. Michael Copenhaver (HIV, intervention) and Carl Latkin (social network analysis, neighborhood effects, intervention) as co-mentors. I will further consult Drs. Ofer Harel for biostatistics, Lesie Snyder for health communication, and Michael Emch for geographical theories of health research. The training will provide opportunities to conduct two research projects for vulnerable drug users with HIV infection. Study 1: To inform the development of an intervention by examining multidimensional (individual- social-ecological) correlates of adherence to ART, retention in care, and HIV treatment outcomes among drug using HIV positive population. [Year 1, 2, 3 (Part)] This is a secondary analysis using data from a randomized controlled trial (Project STRIDE, Altice, R01 DA030768) and its 'Social Network and Neighborhood' Supplement. To this I add the following aims: Specific Aim 1: Extend social network metrics (i.e., derived from network structure) to spatial-social metrics (based on both network structure and spatial proximity between subjects and their network members). Specific Aim 2: Visualize and map the 'activity space' patterns of subjects in a Geographic Information Science interface, including visits to routine locations of positive and negative influence. This is significantly different tha the just the residential location of the subjects. Specific Aim 3: Examine the combined effect of individual, social relationships, activity space, and neighborhood correlates of adherence to ART, retention, and HIV treatment outcomes modeled on a robust multidimensional social-ecological framework. Study 2: To develop and pilot a spatial-network driven intervention with short message services (SMS) that will optimize adherence to ART, retention in care, and HIV treatment outcomes for HIV positive drug users. [Year 3(Part), 4, 5] Phase 1: Select social network members (or alters) who will have stronger effect on the subjects (or egos) adherence to ART, retention, and HIV treatment outcomes. Formative evaluations of ego's activity space and composition and features of their social networks from Study 1 will determine the selection protocol. Phase 2: Conduct a pilot to test the feasibility, acceptability, and preliminary efficacyof a novel spatial- network driven intervention with SMS. The intervention has three arms: 1) Ego in HIV care with two alters assigned highest Interaction Index value, living inside ego's activity space receiving SMS, 2) Egos in HIV care with two alters assigned highest Interaction Index values, living outside the activity space receiving SMS, and 3) Egos in HIV care with no intervention (observational arm).